The present invention pertains to a process for drilling at least two holes in a workpiece in a two-step cycle by means of at least one double-spindle machining unit.
Two machining variants of simultaneously drilling two holes in a workpiece have been known in practice. They are:
Variant 1: Drilling with the use of double-spindle machining centers, or
Variant 2: Drilling on two-way drills.
In Variant 1, two holes are drilled simultaneously in a workpiece in each cycle. The distance between the centers of the two holes is equal to the distance between the axes of the tool spindles. However, the distance between the axes of the tool spindles is not variable, especially in machine tools of a simple design. However, this means that different workpieces with different distances between the centers of the holes would have to be machined on different machine tools, which would lead to high investment cost for a comparatively slight change. An alternative could be at best the use of new bearings for the tool spindles, and these bearings would be weaker in the case of a smaller distance between the holes in the workpiece. However, the effort necessary for this is rather high and also undesirable, because a weakening of the tool spindle bearing as a whole is disadvantageous. The flexibility of the machining possibilities is thus very greatly limited in the case of the machining of workpieces with double-spindle machining centers.
In Variant 2, two workpieces are machined simultaneously by two machining units acting usually in opposite directions due to the movement of a duplicate work holding fixture in two-step cycle. Even though the flexibility of this technological process is substantially higher than that of the above-described Variant 1, two finished workpieces are present here after each cycle of the machine, and these workpieces must be removed and reloaded simultaneously. This requires a high level of technical effort for the upstream and downstream units and/or machining stations.
The basic technical problem of the present invention is to change the technological process of drilling at least two holes in a workpiece such that while the flexibility and the output of the machine are high, simpler peripheral means can be used.
A device for carrying out the process according to the present invention has, to begin with, at least one double-spindle machining unit, which is simultaneously movable along a first travel axis, and a linear carriage unit with a duplicate work holding fixture for two workpieces, which can be moved along a second travel axis independently from the machining unit. The technical problem is accomplished according to the present invention by first drilling a first hole in a first workpiece in a first cycle, after which a second hole is drilled in the first workpiece and a first hole is simultaneously drilled in a second workpiece in a second cycle.
Once this second cycle has been concluded as well, the first workpiece is removed from the duplicate work holding fixture and the duplicate work holding fixture is loaded with another workpiece. A second hole is now drilled in the second workpiece and a first hole is drilled in the workpiece loaded last. The workpieces are machined one after another, and a completely machined workpiece is removed after each work cycle beginning from the second cycle, and the duplicate work holding fixture is loaded with a new workpiece (blank).
Such a process offers the advantages of a higher flexibility along with a simultaneous simplification of the design of the peripheral means as they are usually used in double-spindle machining centers, corresponding to the above-described prior-art Variant 1.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.